I adhere to the following definition of theology offered by John Frame:

I would suggest that we define theology as “the application of the Word of God by
persons to all areas of life.”

Frame gives several advantages to this definition which are worth quoting at length:

1). It gives a clear justification
for the work of theology. Theology is
not needed to remedy formal or material defects in Scripture but to remedy
defects in ourselves, the hearers and readers of Scripture.

2). Theology in this sense has a
clear Scriptural warrant: Scripture commands us to teach in this way (cf. Matt.
28:19f, and many other passages).

3). Despite its focus on human
need, this definition does full justice to the authority and sufficiency of
Scripture. Sola Scriptura does not require that human needs be ignored in
theology, only that Scripture have the final say about the answers to those
needs (and about the propriety of the questions presented).

4). Theology is thus freed from any
false intellectualism or academicism. It
is able to use scientific methods and academic knowledge where they are
helpful, but it can also speak in nonacademic ways, as Scripture itself does –
exhorting, questioning, telling parables, fashioning allegories and poems and
proverbs and songs, expressing love, joy, pateience . . . the list is without
limit.

5). This definition enables us to
make use of data from natural revelation and from man himself.

Frame’s definition makes theology no longer the exclusive domain of the theologian or pastor, but extends it into the domains of mechanics and managers, housewives and teenagers, athletes and
artists, and ballerinas and surfer dudes.